Paint guns with a nozzle assembly having one central nozzle for a mixture of air and paint and other nozzles for air that change the shape of the paint spray fan are well known. The air nozzles direct air into the mixture of air and paint leaving the central nozzle. The air from the air nozzles mixes with the paint and air leaving the central nozzle and changes the shape of the paint spray fan. Adjustments are provided to vary the pressure of air supplied to the air nozzles and thereby adjust the size and shape of the paint spray fan. The nozzle assembly is generally rotatable relative to the nozzle assembly holder to change the orientation of the paint spray fan. Air nozzles that direct air against opposite sides of a stream of paint and air passing through a central nozzle reduce the width of the spray fan in one direction and spread the spray fan in another direction to create an oval spray fan. The dimensions of the oval spray fan can be changed by changing the pressure of the air supplied to the air nozzles. The volume of air mixed with paint can vary over a relatively wide range without adversely affecting a paint spray system. The orientation of the spray fan can be changed by rotating the nozzle assembly relative to a nozzle assembly holder.
Nozzle assemblies are available with a central nozzle that sprays a resin and other nozzles which spray a catalyst into the resin and change the shape of the resin spray fan. The primary function of such nozzle assemblies is to mix the resin and the catalyst. These nozzle assemblies cannot make significant changes in the resin spray fan without adding too much or too little catalyst to the resin. To eliminate waste and reduce cost it is desirable to provide a correct quantity of catalyst to activate the resin. Excess catalyst sprayed into the resin will be wasted and spraying an inadequate quantity of a catalyst will result in incomplete activation of the resin.
The mixture of a gas or liquid with a liquid sprayed from a primary nozzle is undesirable in some processes. When making a urethane foam, for example, by a reaction injection molding process, liquid urethane prepolymers are sprayed onto a substrate and then heat is applied in a mold to cure the polymer. A gas mixed with the liquid is undesirable. Such a gas can interfere with heat transferred during curing and may cause voids in the urethane foam. Current systems for spraying liquid urethane polymers on a substrate either apply the liquid through a nozzle with a small spray fan or apply liquid through a nozzle with a large spray fan. The spray fans are not adjustable during operation. Nozzles with a small spray fan take longer to apply a liquid urethane prepolymer. Nozzles with a relatively large spray fan over spray and waste material when spraying on small areas of a substrate. It is undesirable to apply a liquid prepolymer at a relatively slow rate on large flat areas of a substrate or to waste liquid polymer through over spray when applying a liquid prepolymer to a small area of a substrate.